Introduction to Brake Booster (Vacuum Booster)

Brake assist, aka vacuum booster, is an important part of the car's braking system. Its main role is to amplify the force of the brake pedal, helping the driver easily control the vehicle when needing to decelerate or stop. It plays a key role in improving braking efficiency and enhancing driver safety.

Location and function

Location: Located between the brake pedal and master cylinder

Main function:

• Reduces reaction force from the brake pedal
• Amplifies pressure from the brake pedal
• Helps the driver perform braking operations more gently

Thanks to the booster, the brake system (including brake pads and brake discs) can operate at maximum efficiency without requiring the driver to apply too much force on the pedal.

Principle of operation

The brake booster operates on the principle of pressure difference between atmospheric pressure and vacuum in two separate chambers. This process creates a strong force proportional to the pressure of the pedal.

1. Main components

• Air valve
• Valve control lever
• Air valve feedback spring
• Regulating valve
• Adjusting valve spring
• Power piston
• Constant pressure chamber
• Variable pressure chamber

2. Operational process

Rest state:

• The vacuum valve is separate from the regulating valve
• The two chambers are connected, there is no pressure difference

When applying the brake:

• The control lever pushes the air valve to the left
• The regulator valve contacts the vacuum valve, separating the two chambers
• Outside air enters the variable pressure chamber

Create support:

• The pressure difference between the two chambers pushes the power piston to the left
• Need to push the booster to move, increasing the braking force

Maintain braking force:

• The control valve moves with the piston, blocking air from entering the variable pressure chamber
• Stable pressure, maintaining braking force

Maximum Braking:

• The air valve is completely separated from the control valve
• The variable pressure chamber is filled with air, creating the largest pressure difference
• Achieve maximum support

Common damages

Loss of brake assist:

• Symptoms: Brakes feel heavy
• Cause: The booster is not working

Braking slowly or not braking:

• Symptoms: Stopping distance is longer than usual
• Cause: Braking force is not amplified

Brake pedal abnormality:

• Symptoms: Pedals are higher or lower than normal
• Cause: The power steering valve has a problem

The car jerks when braking:

• Symptoms: Vibration, jerking when braking
• Cause: The diaphragm in the power steering bulb is open or punctured

The brake booster is an important part of the car's safety system. Understanding the operating mechanism and signs of damage helps car owners detect problems early, ensure driving safety and prolong the life of the brake system.

Frequently asked questions

1. How long can a brake booster be in operation before needing maintenance or replacement?

Normally, the brake booster can operate effectively for about 150.000 to 200.000 km, depending on usage conditions and product quality. However, it is recommended to have it checked every 50.000 km to ensure optimal performance. About 10% of vehicles need to replace the power steering valve before 100.000 km due to factors such as harsh environmental conditions or frequent use. Read the article now: Signs of broken brake booster – The most accurate and simple causes and ways to identify are shared on the website.

2. How to distinguish between brake booster failure and other brake system problems?

To differentiate, pay attention to the following characteristic signs:

• Damaged booster: The brake pedal is hard, requiring a lot of force to brake
• Worn brake pads: Metallic noise when braking
• Deformed brake disc: Steering wheel shakes when braking
• Hydraulic system leak: Brake pedal "mushy", falling to the floor

About 75% of poor braking results are due to problems with the booster or brake pads.

3. Does the brake booster have any effect on the anti-lock braking system (ABS)?

The brake booster and ABS system operate independently but complement each other:

• The booster increases braking force, ABS regulates brake pressure
• A damaged booster bulb can reduce the effectiveness of ABS by 30-40%.
• Modern ABS can partially compensate for ineffective power steering

About 95% of modern cars are equipped with both power steering and ABS to optimize braking performance.

4. Is there any difference between the brake booster on gasoline engine vehicles and electric vehicles?

There are significant differences:

• Electric vehicles often use electric boosters instead of vacuum
• Electric power steering efficiency is 20-25% higher than vacuum type
• The electric booster integrates better with the regenerative braking system
• Longer electric power steering bulb life, average 250.000-300.000 km

About 80% of electric vehicles today use electric power steering due to its advantages in performance and integration.